This invention relates to an ink unit for a printing press and method and, more particularly, to a novel arrangement of end seals on the ink fountain associated with a cylindrical transfer roll, i.e., the anilox roll.
In the past, a common practice has been to run the end dams on ink chambers with a small, fixed gap from the anilox roll surface. In this way, the majority of ink would return to the reservoir via the return line and a minor amount would pass through the end dams and return through a catch pan. This provided adequate printing performance but proved "messy", i.e., the uncontained ink must be cleaned off of several surfaces after the printing job is finished.
Representative of the attempts to solve this problem are U.S. Pat. Nos. 4,581,995 and 4,590,855. However, these involve relatively complex mechanisms which substitute cost and other problems for the basic problem.
The main technical problem to be overcome in an end seal is to provide adequate sealing force to overcome the ink chamber static pressure without interfering with the doctor blade loading. The doctor blade loading must be consistent across the anilox roll, right up to the end seal, so that the full roll width may be used for printing. Compounding the problem is doctor blade wear which must allow the doctor blade holder to move closer to the anilox roll to maintain the same doctor blade loading throughout the life of the blade.
According to the invention, a flexible member, shaped to the anilox roll curvature is supported in the ends of the doctor blade holder. The material is advantageously the same as the doctor blade material, preferably plastic, to provide good wear characteristics.
The end seal member is mounted at an angle so that, like the doctor blades, it can flex when the doctor blade assembly is forced against the roll. The angle is chosen so that the resulting stiffening (increase in force for increase in deflection) is roughly the same as the doctor blade stiffness. The angle is further chosen to tip the seal inward so that a component of the static pressure from the ink supply will add to the seal loading, i.e., higher pressures cause higher seal forces.
A number of benefits accrue from the practice of the invention including:
1. No anilox roll modifications needed--the seal rides directly on the engraved or unengraved roll surface;
2. Simple in construction and installation--no adjustments are required;
3. Allows for doctor blade wear--the seal does not interfere with doctor blade loading;
4 The seal can be adapted to a wide range of ink chamber designs;
5. The seal increases sealing force with increase in ink chamber static pressure; and
6. The seal is available at low cost and maintenance.
Other objects and advantages of the invention may be seen in the details in the ensuing specification.